1. Field of the Invention
The present invention relates to a nasally administrable composition containing a physiologically active substance, which attains high stability in the form of a preparation and improved absorbability of said physiologically active substance into the body, when administered nasally.
2. Description of the Prior Art
Physiologically active peptides such as calcitonin and insulin are polymers which are extensively employed for medical usage in clinical practice, due to their specific physiological activity.
These physiologically active peptides, however, can little be absorbed intact from the mucous membrane of the intestine because they are likely to be decomposed with proteases existing in the digestive system or are high in molecular weight and polarity. Hence, they cannot be administered orally and they can be administered only through injection. The injectable administration cannot be said to be preferable because the injection causes pain at the site of injection to patients. In addition, particularly, when the injection should be repeated at constant intervals, such pain is repeated whenever they are injected and it may often become too severe for patients to endure. Therefore, strong demand has been made to develop a method for administering the physiologically active peptide via a non-injection route and, more preferably, a method which enable patients to administer it by themselves, which further should be safe, simple in administration and administrable with less frequency.
As one of such methods for administering the physiologically active peptides, an aerosol in the form of a suspension, which uses a fluorinated hydrocarbon as a spouting agent, has been developed for nasally administering, for example, calcitonin. As another means for nasal administration, a spraying agent has been proposed as a nasally administrable liquid preparation, which is a preparation in which calcitonin is formulated with a surface-active agent as an absorption promoter. Furthermore, recently, there have been proposed some nasally administrable powdery preparations having improved absorbability, which are prepared by adsorbing calcitonin onto a polysaccharide such as cellulose.
On the other hand, up to now, there have been developed a great many synthetic medicaments for various therapeutical purposes; however, there have not been developed into datails for nasally administrable preparations containing said medicaments.
The various techniques for nasal administration, which have most recently been actively developed, are said to be in principle superior as methods for administering such physiologically active peptides as unlikely to be administered orally or as well as for administering such synthetic medicaments. Since the plexus venosus develops at the nasal lamina propria mucosae of the nasal cavity, the physiologically active peptide or the synthetic medicament, when administered nasally, is absorbed through the mucous membrane of the nasal cavity into the circulatory system of the body; however, nasally administrable preparations so far proposed are not satisfactory because of poor absorbability of the active ingredient or local irritation so that they are not commercially available yet.